/******************************************************************************

  Copyright (C), 2012-2016, ZHANGYA

 ******************************************************************************
  File Name     : ztime.c
  Version       : Initial Draft
  Author        : zhangya
  Created       : 2024/5/16
  Last Modified :
  Description   : ztime.c
  Function List :
  History       :
  1.Date        : 2024/5/16
    Author      : zhangya
    Modification: Created file

******************************************************************************/
#include "ztime.h"
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>

/*--------------------------------------------------------------------*
 * $external variables                           *
 *--------------------------------------------------------------------*/

/*--------------------------------------------------------------------*
 * $external routine prototypes                  *
 *--------------------------------------------------------------------*/

/*
 * We do not implement alternate representations. However, we always
 * check whether a given modifier is allowed for a certain conversion.
 */
#define ALT_E     		0x01
#define ALT_O     		0x02
#define LEGAL_ALT(x)    { if (alt_format & ~(x)) return (0); }

/*--------------------------------------------------------------------*
 * $internal routine prototypes                  *
 *--------------------------------------------------------------------*/

/*--------------------------------------------------------------------*
 * $project-wide global variables                *
 *--------------------------------------------------------------------*/
static const char *day[7] = {
  "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday",
  "Friday", "Saturday"
};
static const char *abday[7] = {
  "Sun","Mon","Tue","Wed","Thu","Fri","Sat"
};
static const char *mon[12] = {
  "January", "February", "March", "April", "May", "June", "July",
  "August", "September", "October", "November", "December"
};
static const char *abmon[12] = {
  "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};
static const char *am_pm[2] = {
  "AM", "PM"
};

/*--------------------------------------------------------------------*
 * $module-wide global variables                 *
 *--------------------------------------------------------------------*/

/*--------------------------------------------------------------------*
 * $constants                                    *
 *--------------------------------------------------------------------*/
static  int conv_num(const char **, int *, int, int);

/*--------------------------------------------------------------------*
 * $macros                                       *
 *--------------------------------------------------------------------*/

/*--------------------------------------------------------------------*
 * $routines' implementations                    *
 *--------------------------------------------------------------------*/

static int conv_num(const char **buf, int *dest, int llim, int ulim)
{
	int result = 0;

	/* The limit also determines the number of valid digits. */
	int rulim = ulim;

	if (**buf < '0' || **buf > '9')
		return (0);

	do {
		result *= 10;
		result += *(*buf)++ - '0';
		rulim /= 10;
	} while ((result * 10 <= ulim) && rulim && **buf >= '0' && **buf <= '9');

	if (result < llim || result > ulim)
		return (0);

	*dest = result;
	return (1);
}


char * strptime(const char *buf, const char *fmt, struct tm *tm)
{
  char c;
  const char *bp;
  size_t len = 0;
  int alt_format, i, split_year = 0;
 
  bp = buf;
 
  while ((c = *fmt) != '\0') {
    /* Clear `alternate' modifier prior to new conversion. */
    alt_format = 0;
 
    /* Eat up white-space. */
    if (isspace(c)) {
      while (isspace(*bp))
        bp++;
 
      fmt++;
      continue;
    }
        
    if ((c = *fmt++) != '%')
      goto literal;
 
 
again:    switch (c = *fmt++) {
    case '%': /* "%%" is converted to "%". */
literal:
      if (c != *bp++)
        return (0);
      break;
 
    /*
     * "Alternative" modifiers. Just set the appropriate flag
     * and start over again.
     */
    case 'E': /* "%E?" alternative conversion modifier. */
      LEGAL_ALT(0);
      alt_format |= ALT_E;
      goto again;
 
    case 'O': /* "%O?" alternative conversion modifier. */
      LEGAL_ALT(0);
      alt_format |= ALT_O;
      goto again;
      
    /*
     * "Complex" conversion rules, implemented through recursion.
     */
    case 'c': /* Date and time, using the locale's format. */
      LEGAL_ALT(ALT_E);
	  bp = strptime(bp, "%x %X", tm);
      if (bp != NULL)
      	return (0);
      break;
 
    case 'D': /* The date as "%m/%d/%y". */
      LEGAL_ALT(0);
	  bp = strptime(bp, "%m/%d/%y", tm);
      if (bp != NULL)
        return (0);
      break;
 
    case 'R': /* The time as "%H:%M". */
      LEGAL_ALT(0);
	  bp = strptime(bp, "%H:%M", tm);
      if (bp != NULL)
        return (0);
      break;
 
    case 'r': /* The time in 12-hour clock representation. */
      LEGAL_ALT(0);
	  bp = strptime(bp, "%I:%M:%S %p", tm);
      if (bp != NULL)
        return (0);
      break;
 
    case 'T': /* The time as "%H:%M:%S". */
      LEGAL_ALT(0);
	  bp = strptime(bp, "%H:%M:%S", tm);
      if (bp != NULL)
        return (0);
      break;
 
    case 'X': /* The time, using the locale's format. */
      LEGAL_ALT(ALT_E);
	  bp = strptime(bp, "%H:%M:%S", tm);
      if (bp != NULL)
        return (0);
      break;
 
    case 'x': /* The date, using the locale's format. */
      LEGAL_ALT(ALT_E);
	  bp = strptime(bp, "%m/%d/%y", tm);
      if (bp != NULL)
        return (0);
      break;
 
    /*
     * "Elementary" conversion rules.
     */
    case 'A': /* The day of week, using the locale's form. */
    case 'a':
      LEGAL_ALT(0);
      for (i = 0; i < 7; i++) {
        /* Full name. */
        len = strlen(day[i]);
        if (strncmp(day[i], bp, len) == 0)
          break;
 
        /* Abbreviated name. */
        len = strlen(abday[i]);
        if (strncmp(abday[i], bp, len) == 0)
          break;
      }
 
      /* Nothing matched. */
      if (i == 7)
        return (0);
 
      tm->tm_wday = i;
      bp += len;
      break;
 
    case 'B': /* The month, using the locale's form. */
    case 'b':
    case 'h':
      LEGAL_ALT(0);
      for (i = 0; i < 12; i++) {
        /* Full name. */
        len = strlen(mon[i]);
        if (strncmp(mon[i], bp, len) == 0)
          break;
 
        /* Abbreviated name. */
        len = strlen(abmon[i]);
        if (strncmp(abmon[i], bp, len) == 0)
          break;
      }
 
      /* Nothing matched. */
      if (i == 12)
        return (0);
 
      tm->tm_mon = i;
      bp += len;
      break;
 
    case 'C': /* The century number. */
      LEGAL_ALT(ALT_E);
      if (!(conv_num(&bp, &i, 0, 99)))
        return (0);
 
      if (split_year) {
        tm->tm_year = (tm->tm_year % 100) + (i * 100);
      } else {
        tm->tm_year = i * 100;
        split_year = 1;
      }
      break;
 
    case 'd': /* The day of month. */
    case 'e':
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &tm->tm_mday, 1, 31)))
        return (0);
      break;
 
    case 'k': /* The hour (24-hour clock representation). */
      LEGAL_ALT(0);
      /* FALLTHROUGH */
    case 'H':
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &tm->tm_hour, 0, 23)))
        return (0);
      break;
 
    case 'l': /* The hour (12-hour clock representation). */
      LEGAL_ALT(0);
      /* FALLTHROUGH */
    case 'I':
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &tm->tm_hour, 1, 12)))
        return (0);
      if (tm->tm_hour == 12)
        tm->tm_hour = 0;
      break;
 
    case 'j': /* The day of year. */
      LEGAL_ALT(0);
      if (!(conv_num(&bp, &i, 1, 366)))
        return (0);
      tm->tm_yday = i - 1;
      break;
 
    case 'M': /* The minute. */
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &tm->tm_min, 0, 59)))
        return (0);
      break;
 
    case 'm': /* The month. */
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &i, 1, 12)))
        return (0);
      tm->tm_mon = i - 1;
      break;
 
    case 'p': /* The locale's equivalent of AM/PM. */
      LEGAL_ALT(0);
      /* AM? */
      if (strcmp(am_pm[0], bp) == 0) {
        if (tm->tm_hour > 11)
          return (0);
 
        bp += strlen(am_pm[0]);
        break;
      }
      /* PM? */
      else if (strcmp(am_pm[1], bp) == 0) {
        if (tm->tm_hour > 11)
          return (0);
 
        tm->tm_hour += 12;
        bp += strlen(am_pm[1]);
        break;
      }
 
      /* Nothing matched. */
      return (0);
 
    case 'S': /* The seconds. */
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &tm->tm_sec, 0, 61)))
        return (0);
      break;
 
    case 'U': /* The week of year, beginning on sunday. */
    case 'W': /* The week of year, beginning on monday. */
      LEGAL_ALT(ALT_O);
      /*
       * XXX This is bogus, as we can not assume any valid
       * information present in the tm structure at this
       * point to calculate a real value, so just check the
       * range for now.
       */
       if (!(conv_num(&bp, &i, 0, 53)))
        return (0);
       break;
 
    case 'w': /* The day of week, beginning on sunday. */
      LEGAL_ALT(ALT_O);
      if (!(conv_num(&bp, &tm->tm_wday, 0, 6)))
        return (0);
      break;
 
    case 'Y': /* The year. */
      LEGAL_ALT(ALT_E);
      if (!(conv_num(&bp, &i, 0, 9999)))
        return (0);
 
      tm->tm_year = i - TM_YEAR_BASE;
      break;
 
    case 'y': /* The year within 100 years of the epoch. */
      LEGAL_ALT(ALT_E | ALT_O);
      if (!(conv_num(&bp, &i, 0, 99)))
        return (0);
 
      if (split_year) {
        tm->tm_year = ((tm->tm_year / 100) * 100) + i;
        break;
      }
      split_year = 1;
      if (i <= 68)
        tm->tm_year = i + 2000 - TM_YEAR_BASE;
      else
        tm->tm_year = i + 1900 - TM_YEAR_BASE;
      break;
 
    /*
     * Miscellaneous conversions.
     */
    case 'n': /* Any kind of white-space. */
    case 't':
      LEGAL_ALT(0);
      while (isspace(*bp))
        bp++;
      break;
 
 
    default:  /* Unknown/unsupported conversion. */
      return (0);
    }
  }
  /* LINTED functional specification */
  return ((char *)bp);
}


